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ADP5520 Not Recommended for New Designs
The ADP5520 is a versatile single-chip, white LED backlight driver with a user configurable I/O expander. This device fits handset applications where the...
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ADP5520 on Analog.com

Associated Drivers

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Using ADP5520 for driving SHARP LCD backlight

		
	
				

			

									
					    Ashish
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Apr 9, 2012 
				
			
			
		

		
		                     
				
        		

		    
		    		    
		    			

			    
Hi,

 
We are planning to use the ADP5520 Backlight driving chip for our LCD panel - SHARP - LQ043T3DG01. Datasheet can be downloaded from here: 

 
http://www.google.co.in/url?sa=t&rct=j&q=sharp%20lq043t3dg01&source=web&cd=1&ved=0CDAQFjAA&url=http%3A%2F%2Fwww.sharpsme.com%2Fdownload%2FLQ043T3DG01-SPpdf&ei=5caCT6WoCpHMrQfvksHeBQ&usg=AFQjCNE8xPyTp0LW6AXB_0xxWSb0adR61Q&cad=rja

 
Could someone please confirm if ADP5520 can drive the backlight for the above display. The chip datasheet mentions the right voltage range needed but it also says it can support only upto 6 LEDs while this SHARP display has 9 LEDs. Should it make the difference as long as the voltage is within range?

 
Best regards,

 
Ashish

			

			
									
		                             
                        

    

                                            
                 backlight
                
                                                    
                 Controllers/Expanders
                
                                                    
                 lcd
                
                                                    
                 adp5520
                
                                                    
                 Mobile I/O Expander and Keypad Controller
                
                                
            

    
    
		


				
				        
        		

			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		


        
        
        
    
					

			





















	

	

					



			


				
	









	
    
	

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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Apr 9, 2012 4:27 PM
            
            
						
			            		
    
		
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    Hi Ashish,
    
 
    As far as I can see, from the SHARP documentation, the LED max forward voltage for 9 LEDs in series is 31.5V while the typ. is 28.8V, assuming 20mA driving current. The ADP5520 has an over-voltage protection circuit (OVP) set to 27V (29.5V max), this means that driving the module with 20mA the ADP5520 will likely enter in OVP where the boost circuit will be disabled until the voltage on BST pin falls below OVP limit, minus some hysteresis. In this mode of operation the LED average current will be severely limited.
    
 
    If your application allows, you can consider to decrease the LED current so that the total VF voltage for the 9 LEDs is below OVP level across temperature and lot to lot variations, this is something you will need to check with SHARP or Nichia.
    
 
    Please let me know if you need additional information. Thanks
    
 
    Best regards,
    
 
    Maurizio
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
				
				
				
		
		
    
			
		
    
	
    

    

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